package im.actor.runtime.crypto.primitives.curve25519;

// Disabling Bounds checks for speeding up calculations

/*-[
#define J2OBJC_DISABLE_ARRAY_BOUND_CHECKS 1
]-*/

public class fe_mul {

//CONVERT #include "fe.h"
//CONVERT #include "long.h"

/*
h = f * g
Can overlap h with f or g.

Preconditions:
   |f| bounded by 1.65*2^26,1.65*2^25,1.65*2^26,1.65*2^25,etc.
   |g| bounded by 1.65*2^26,1.65*2^25,1.65*2^26,1.65*2^25,etc.

Postconditions:
   |h| bounded by 1.01*2^25,1.01*2^24,1.01*2^25,1.01*2^24,etc.
*/

/*
Notes on implementation strategy:

Using schoolbook multiplication.
Karatsuba would save a little in some cost models.

Most multiplications by 2 and 19 are 32-bit precomputations;
cheaper than 64-bit postcomputations.

There is one remaining multiplication by 19 in the carry chain;
one *19 precomputation can be merged into this,
but the resulting data flow is considerably less clean.

There are 12 carries below.
10 of them are 2-way parallelizable and vectorizable.
Can get away with 11 carries, but then data flow is much deeper.

With tighter constraints on inputs can squeeze carries into int32.
*/

    private static long[] fe_mul1(int[] f, int[] g) {
        int f0 = f[0];
        int f1 = f[1];
        int f2 = f[2];
        int f3 = f[3];
        int f4 = f[4];
        int f5 = f[5];
        int f6 = f[6];
        int f7 = f[7];
        int f8 = f[8];
        int f9 = f[9];
        int g0 = g[0];
        int g1 = g[1];
        int g2 = g[2];
        int g3 = g[3];
        int g4 = g[4];
        int g5 = g[5];
        int g6 = g[6];
        int g7 = g[7];
        int g8 = g[8];
        int g9 = g[9];
        int g1_19 = 19 * g1; /* 1.959375*2^29 */
        int g2_19 = 19 * g2; /* 1.959375*2^30; still ok */
        int g3_19 = 19 * g3;
        int g4_19 = 19 * g4;
        int g5_19 = 19 * g5;
        int g6_19 = 19 * g6;
        int g7_19 = 19 * g7;
        int g8_19 = 19 * g8;
        int g9_19 = 19 * g9;
        int f1_2 = 2 * f1;
        int f3_2 = 2 * f3;
        int f5_2 = 2 * f5;
        int f7_2 = 2 * f7;
        int f9_2 = 2 * f9;
        long f0g0 = f0 * (long) g0;
        long f0g1 = f0 * (long) g1;
        long f0g2 = f0 * (long) g2;
        long f0g3 = f0 * (long) g3;
        long f0g4 = f0 * (long) g4;
        long f0g5 = f0 * (long) g5;
        long f0g6 = f0 * (long) g6;
        long f0g7 = f0 * (long) g7;
        long f0g8 = f0 * (long) g8;
        long f0g9 = f0 * (long) g9;
        long f1g0 = f1 * (long) g0;
        long f1g1_2 = f1_2 * (long) g1;
        long f1g2 = f1 * (long) g2;
        long f1g3_2 = f1_2 * (long) g3;
        long f1g4 = f1 * (long) g4;
        long f1g5_2 = f1_2 * (long) g5;
        long f1g6 = f1 * (long) g6;
        long f1g7_2 = f1_2 * (long) g7;
        long f1g8 = f1 * (long) g8;
        long f1g9_38 = f1_2 * (long) g9_19;
        long f2g0 = f2 * (long) g0;
        long f2g1 = f2 * (long) g1;
        long f2g2 = f2 * (long) g2;
        long f2g3 = f2 * (long) g3;
        long f2g4 = f2 * (long) g4;
        long f2g5 = f2 * (long) g5;
        long f2g6 = f2 * (long) g6;
        long f2g7 = f2 * (long) g7;
        long f2g8_19 = f2 * (long) g8_19;
        long f2g9_19 = f2 * (long) g9_19;
        long f3g0 = f3 * (long) g0;
        long f3g1_2 = f3_2 * (long) g1;
        long f3g2 = f3 * (long) g2;
        long f3g3_2 = f3_2 * (long) g3;
        long f3g4 = f3 * (long) g4;
        long f3g5_2 = f3_2 * (long) g5;
        long f3g6 = f3 * (long) g6;
        long f3g7_38 = f3_2 * (long) g7_19;
        long f3g8_19 = f3 * (long) g8_19;
        long f3g9_38 = f3_2 * (long) g9_19;
        long f4g0 = f4 * (long) g0;
        long f4g1 = f4 * (long) g1;
        long f4g2 = f4 * (long) g2;
        long f4g3 = f4 * (long) g3;
        long f4g4 = f4 * (long) g4;
        long f4g5 = f4 * (long) g5;
        long f4g6_19 = f4 * (long) g6_19;
        long f4g7_19 = f4 * (long) g7_19;
        long f4g8_19 = f4 * (long) g8_19;
        long f4g9_19 = f4 * (long) g9_19;
        long f5g0 = f5 * (long) g0;
        long f5g1_2 = f5_2 * (long) g1;
        long f5g2 = f5 * (long) g2;
        long f5g3_2 = f5_2 * (long) g3;
        long f5g4 = f5 * (long) g4;
        long f5g5_38 = f5_2 * (long) g5_19;
        long f5g6_19 = f5 * (long) g6_19;
        long f5g7_38 = f5_2 * (long) g7_19;
        long f5g8_19 = f5 * (long) g8_19;
        long f5g9_38 = f5_2 * (long) g9_19;
        long f6g0 = f6 * (long) g0;
        long f6g1 = f6 * (long) g1;
        long f6g2 = f6 * (long) g2;
        long f6g3 = f6 * (long) g3;
        long f6g4_19 = f6 * (long) g4_19;
        long f6g5_19 = f6 * (long) g5_19;
        long f6g6_19 = f6 * (long) g6_19;
        long f6g7_19 = f6 * (long) g7_19;
        long f6g8_19 = f6 * (long) g8_19;
        long f6g9_19 = f6 * (long) g9_19;
        long f7g0 = f7 * (long) g0;
        long f7g1_2 = f7_2 * (long) g1;
        long f7g2 = f7 * (long) g2;
        long f7g3_38 = f7_2 * (long) g3_19;
        long f7g4_19 = f7 * (long) g4_19;
        long f7g5_38 = f7_2 * (long) g5_19;
        long f7g6_19 = f7 * (long) g6_19;
        long f7g7_38 = f7_2 * (long) g7_19;
        long f7g8_19 = f7 * (long) g8_19;
        long f7g9_38 = f7_2 * (long) g9_19;
        long f8g0 = f8 * (long) g0;
        long f8g1 = f8 * (long) g1;
        long f8g2_19 = f8 * (long) g2_19;
        long f8g3_19 = f8 * (long) g3_19;
        long f8g4_19 = f8 * (long) g4_19;
        long f8g5_19 = f8 * (long) g5_19;
        long f8g6_19 = f8 * (long) g6_19;
        long f8g7_19 = f8 * (long) g7_19;
        long f8g8_19 = f8 * (long) g8_19;
        long f8g9_19 = f8 * (long) g9_19;
        long f9g0 = f9 * (long) g0;
        long f9g1_38 = f9_2 * (long) g1_19;
        long f9g2_19 = f9 * (long) g2_19;
        long f9g3_38 = f9_2 * (long) g3_19;
        long f9g4_19 = f9 * (long) g4_19;
        long f9g5_38 = f9_2 * (long) g5_19;
        long f9g6_19 = f9 * (long) g6_19;
        long f9g7_38 = f9_2 * (long) g7_19;
        long f9g8_19 = f9 * (long) g8_19;
        long f9g9_38 = f9_2 * (long) g9_19;
        long h[] = new long[10];
        h[0] = f0g0 + f1g9_38 + f2g8_19 + f3g7_38 + f4g6_19 + f5g5_38 + f6g4_19 + f7g3_38 + f8g2_19 + f9g1_38;
        h[1] = f0g1 + f1g0 + f2g9_19 + f3g8_19 + f4g7_19 + f5g6_19 + f6g5_19 + f7g4_19 + f8g3_19 + f9g2_19;
        h[2] = f0g2 + f1g1_2 + f2g0 + f3g9_38 + f4g8_19 + f5g7_38 + f6g6_19 + f7g5_38 + f8g4_19 + f9g3_38;
        h[3] = f0g3 + f1g2 + f2g1 + f3g0 + f4g9_19 + f5g8_19 + f6g7_19 + f7g6_19 + f8g5_19 + f9g4_19;
        h[4] = f0g4 + f1g3_2 + f2g2 + f3g1_2 + f4g0 + f5g9_38 + f6g8_19 + f7g7_38 + f8g6_19 + f9g5_38;
        h[5] = f0g5 + f1g4 + f2g3 + f3g2 + f4g1 + f5g0 + f6g9_19 + f7g8_19 + f8g7_19 + f9g6_19;
        h[6] = f0g6 + f1g5_2 + f2g4 + f3g3_2 + f4g2 + f5g1_2 + f6g0 + f7g9_38 + f8g8_19 + f9g7_38;
        h[7] = f0g7 + f1g6 + f2g5 + f3g4 + f4g3 + f5g2 + f6g1 + f7g0 + f8g9_19 + f9g8_19;
        h[8] = f0g8 + f1g7_2 + f2g6 + f3g5_2 + f4g4 + f5g3_2 + f6g2 + f7g1_2 + f8g0 + f9g9_38;
        h[9] = f0g9 + f1g8 + f2g7 + f3g6 + f4g5 + f5g4 + f6g3 + f7g2 + f8g1 + f9g0;

        return h;
    }

    public static void fe_mul(int[] h, int[] f, int[] g) {

        long hr[] = fe_mul1(f, g);

        long carry0;
        long carry1;
        long carry2;
        long carry3;
        long carry4;
        long carry5;
        long carry6;
        long carry7;
        long carry8;
        long carry9;

  /*
  |h0| <= (1.65*1.65*2^52*(1+19+19+19+19)+1.65*1.65*2^50*(38+38+38+38+38))
    i.e. |h0| <= 1.4*2^60; narrower ranges for h2, h4, h6, h8
  |h1| <= (1.65*1.65*2^51*(1+1+19+19+19+19+19+19+19+19))
    i.e. |h1| <= 1.7*2^59; narrower ranges for h3, h5, h7, h9
  */

        carry0 = (hr[0] + (long) (1 << 25)) >> 26;
        hr[1] += carry0;
        hr[0] -= carry0 << 26;
        carry4 = (hr[4] + (long) (1 << 25)) >> 26;
        hr[5] += carry4;
        hr[4] -= carry4 << 26;
  /* |h0| <= 2^25 */
  /* |h4| <= 2^25 */
  /* |h1| <= 1.71*2^59 */
  /* |h5| <= 1.71*2^59 */

        carry1 = (hr[1] + (long) (1 << 24)) >> 25;
        hr[2] += carry1;
        hr[1] -= carry1 << 25;
        carry5 = (hr[5] + (long) (1 << 24)) >> 25;
        hr[6] += carry5;
        hr[5] -= carry5 << 25;
  /* |h1| <= 2^24; from now on fits into int32 */
  /* |h5| <= 2^24; from now on fits into int32 */
  /* |h2| <= 1.41*2^60 */
  /* |h6| <= 1.41*2^60 */

        carry2 = (hr[2] + (long) (1 << 25)) >> 26;
        hr[3] += carry2;
        hr[2] -= carry2 << 26;
        carry6 = (hr[6] + (long) (1 << 25)) >> 26;
        hr[7] += carry6;
        hr[6] -= carry6 << 26;
  /* |h2| <= 2^25; from now on fits into int32 unchanged */
  /* |h6| <= 2^25; from now on fits into int32 unchanged */
  /* |h3| <= 1.71*2^59 */
  /* |h7| <= 1.71*2^59 */

        carry3 = (hr[3] + (long) (1 << 24)) >> 25;
        hr[4] += carry3;
        hr[3] -= carry3 << 25;
        carry7 = (hr[7] + (long) (1 << 24)) >> 25;
        hr[8] += carry7;
        hr[7] -= carry7 << 25;
  /* |h3| <= 2^24; from now on fits into int32 unchanged */
  /* |h7| <= 2^24; from now on fits into int32 unchanged */
  /* |h4| <= 1.72*2^34 */
  /* |h8| <= 1.41*2^60 */

        carry4 = (hr[4] + (long) (1 << 25)) >> 26;
        hr[5] += carry4;
        hr[4] -= carry4 << 26;
        carry8 = (hr[8] + (long) (1 << 25)) >> 26;
        hr[9] += carry8;
        hr[8] -= carry8 << 26;
  /* |h4| <= 2^25; from now on fits into int32 unchanged */
  /* |h8| <= 2^25; from now on fits into int32 unchanged */
  /* |h5| <= 1.01*2^24 */
  /* |h9| <= 1.71*2^59 */

        carry9 = (hr[9] + (long) (1 << 24)) >> 25;
        hr[0] += carry9 * 19;
        hr[9] -= carry9 << 25;
  /* |h9| <= 2^24; from now on fits into int32 unchanged */
  /* |h0| <= 1.1*2^39 */

        carry0 = (hr[0] + (long) (1 << 25)) >> 26;
        hr[1] += carry0;
        hr[0] -= carry0 << 26;
  /* |h0| <= 2^25; from now on fits into int32 unchanged */
  /* |h1| <= 1.01*2^24 */

        h[0] = (int) hr[0];
        h[1] = (int) hr[1];
        h[2] = (int) hr[2];
        h[3] = (int) hr[3];
        h[4] = (int) hr[4];
        h[5] = (int) hr[5];
        h[6] = (int) hr[6];
        h[7] = (int) hr[7];
        h[8] = (int) hr[8];
        h[9] = (int) hr[9];
    }
}
